title: RhoA-dependent phosphorylation and relocalization of ERM proteins into apical membrane/actin protrusions in fibroblasts.
abstract: The ERM proteins (ezrin, radixin, and moesin) are a group of band 4. 1-related proteins that are proposed to function as membrane/cytoskeletal linkers. Previous biochemical studies have implicated RhoA in regulating the association of ERM proteins with their membrane targets. However, the specific effect and mechanism of action of this regulation is unclear. We show that lysophosphatidic acid stimulation of serum-starved NIH3T3 cells resulted in relocalization of radixin into apical membrane/actin protrusions, which was blocked by inactivation of Rho by C3 transferase. An activated allele of RhoA, but not Rac or CDC42Hs, was sufficient to induce apical membrane/actin protrusions and localize radixin or moesin into these structures in both Rat1 and NIH3T3 cells. Lysophosphatidic acid treatment led to phosphorylation of radixin preceding its redistribution into apical protrusions. Significantly, cotransfection of RhoAV14 or C3 transferase with radixin and moesin revealed that RhoA activity is necessary and sufficient for their phosphorylation. These findings reveal a novel function of RhoA in reorganizing the apical actin cytoskeleton and suggest that this function may be mediated through phosphorylation of ERM proteins.
authors.affiliation: Center for Cancer Research, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 12139, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Shaw
authors.forename: M
authors.initials: M
authors.lastname: Henry
authors.forename: F
authors.initials: F
authors.lastname: Solomon
authors.forename: T
authors.initials: T
authors.lastname: Jacks
mesh_terms: D016475:3T3 Cells; D036002:ADP Ribose Transferases / Q000502:physiology; D008841:Actin Cytoskeleton / Q000737:chemistry / Q000187:drug effects; D000199:Actins / Q000032:analysis*; D000818:Animals; D001798:Blood Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D001905:Botulinum Toxins; D002462:Cell Membrane / Q000648:ultrastructure; D003598:Cytoskeletal Proteins; D005347:Fibroblasts / Q000737:chemistry / Q000648:ultrastructure*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000502:physiology*; D018960:Hyaluronan Receptors / Q000032:analysis; D008246:Lysophospholipids / Q000494:pharmacology; D008565:Membrane Proteins / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins; D025581:Neurofibromin 2; D010750:Phosphoproteins / Q000032:analysis; D010766:Phosphorylation; D011506:Proteins / Q000032:analysis / Q000378:metabolism; D020742:rhoA GTP-Binding Protein; D000099149:Ezrin
chemical_list: D036002:ADP Ribose Transferases; D000199:Actins; D001798:Blood Proteins; D001905:Botulinum Toxins; D003598:Cytoskeletal Proteins; D019204:GTP-Binding Proteins; D018960:Hyaluronan Receptors; D008246:Lysophospholipids; D008565:Membrane Proteins; D008840:Microfilament Proteins; D025581:Neurofibromin 2; D010750:Phosphoproteins; D011506:Proteins; D020742:rhoA GTP-Binding Protein; D000099149:Ezrin; C071058:moesin; C071776:radixin; C063007:exoenzyme C3, Clostridium botulinum